Such light scanning devices are used e.g. for examinations in the field of molecular biology or genetic technology. For these examinations, a large number of materials to be examined are applied to a carrier in a fieldlike configuration, whereupon said materials are temporarily brought into contact with a fluorescent tracer. The materials to be examined having an affinity for the tracer will bind said tracer to themselves and can therefore be excited so as to emit fluorescent light. It follows that, due to the excitability of the fluorescence, the property of the examined material to bind to itself the tracer becomes visible, whereby it is possible to draw conclusions with regard to the nature of the sample material.
When examinations in the field of molecular biology or genetic technology are carried out, large fields of such materials marked with fluorescent substances are sequentially scanned with exciting light. In hitherto known devices, the carrier holding the sample materials has been scanned by means of two tilting mirrors provided in the optical path of the exciting light, the two axes of rotation of said tilting mirrors extending at right angles to one another. When the scanning light beam impinges on a location where a marked and, consequently, fluorescent sample material is present secondary light will be emitted, which is detected by a detection unit comprising a detection optics and a detector device, and converted into electric signals.
In such devices the rotation of the tilting mirrors for the purpose of scanning is, however, subject to tolerances, and due to the long beam path this results in major inaccuracies in the local resolution of the scanning. In the case of a "pre-objective-scanning" arrangement of the focussing optics (i.e. between the scanning unit and the sample), it is additionally necessary that said focussing optics has a large diameter so that an image of the light ray bundle deflected from the optical axis by the scanning mirrors can be formed in the plane of the sample. When such large-diameter lenses are used, a correction for large angular fields and a good field flatness is, however, very complicated and entails therefore higher costs.